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Seizure triggers for people with photosensitive epilepsy

There are a number of things that could trigger a photosensitive seizure. Because people’s sensitivities are so individual, not everything will affect every person with photosensitive epilepsy. The following are some of the things that people ask us about:

Bicycle lights (red and white)

UK law says that these lights mustn’t flash at less than one or more than 4 flashes a second. Provided the lights comply with the law, they are unlikely to cause a problem.

Ceiling fans

Some ceiling fans can rotate at a fast speed. Looking at light through them could be a seizure trigger.

Christmas lights that flash

There is no UK law that covers the flash frequency of Christmas lights. It’s therefore possible that they could trigger a seizure.

Computer screens

Computer screens are unlikely to be a seizure trigger. However if there are flashing or flickering images, or some types of pattern on the screen, these could be a seizure trigger.

Flashing novelty badges

These can flash at any rate. It is therefore possible that they could be a seizure trigger.

Interactive whiteboards

Unless what is shown on an interactive whiteboard flashes or flickers, or has some types of pattern, they are unlikely to be a seizure trigger.

Light bulbs (any type)

These are only a possible seizure trigger if they are faulty. Otherwise, they shouldn’t cause a problem.


These are some examples of patterns that could be seizure triggers:

  • High contrast patterns such as black and white stripes
  • Striped or patterned materials and walls
  • Patterns in some television programmes, video or electronic games
  • A moving escalator

Strobe lights

We have been unable to find any current official guidance on the recommended flash rate of strobe lights. However, it is possible that they could be a seizure trigger.

The American Epilepsy Foundation’s professional advisory board recommends that:

  • The flash rate be kept to under 2 hertz with breaks every so often between flashes
  • Flashing lights should be placed at a distance from each other and set to flash together at the same time to avoid an increase in the number of individual flashes

The word hertz refers to something that happens in a second. For example, it can mean the number of times something flashes or flickers in 1 second.


These may trigger a seizure if the tubes flicker. Otherwise, they shouldn't cause a problem.


Looking directly at certain patterns caused by sunlight could be a seizure trigger for some people. Examples of these situations are:

  • Sunlight through slatted blinds
  • Sunlight through trees, viewed from a moving vehicle
  • Sunlight reflected off moving water or off snow
  • Sunlight through moving leaves
  • Sunlight through railings, as you move past them

TV screens

Modern TV screens don’t flicker so are unlikely to be a seizure trigger for most people. However, if a programme shows images that flash or flicker, these could be a seizure trigger for some people.

Wind turbines

Large wind turbines rotate at a rate that is unlikely to trigger a seizure. Smaller turbines can rotate at a faster rate. When these smaller turbines create a shadow and/or flicker effect with the sun, they could be a seizure trigger.

Useful information

If you are concerned about flashing artificial lights, you can complain to your local council. They should consider complaints about ‘nuisance lights’, but they may not take account of someone’s photosensitive epilepsy. This is because they only have to consider how the nuisance affects the ‘average person’, not people with ‘rare sensitivities.’

If you would like to see this information with references, visit the Advice and Information references section of our website or contact our Epilepsy Action freephone Helpline on 0808 800 5050.


This information has been produced under the terms of The Information Standard.

  • Updated June 2018
    To be reviewed June 2021

Comments: read the 7 comments or add yours


Is it possible that very bright sunlight, or rather high UV values as found in Texas where the UV index is often 3 x that in the UK can trigger focal seizures even though on medication and free for over 6 months.

Submitted by Richard Moseley on

Any relation between the older radars and photosensitive seizures??
I have in excess of 25,000 radar hours and was diagnosed at the age of 54 as an epileptic, twenty years ago. I still have epilepsy & have no doubt that radar RF & other aviation, civil & military equipment caused my epilepsy. Is there any on-going research into the link of epilepsy & radar?

Submitted by Bob on

Hi Bob

We aren’t aware of any research between epilepsy and radar.



Epilepsy Action Helpline Team

Submitted by rich on

Can vividly imagining the "flashing lights" you once saw before having a seizure trigger seizures? I imagine a lot of those and the image would linger in my mind as if I had just hallucinated and that causes a worry as to maybe would it catch me just by imagining or thinking about it. And also I read somewhere about photosensitive epilepsy that being tired can trigger seizures. What kind of tiredness do they mean? I want to know is it safe for a person with photosensitive epilepsy participate in sports, exercise or even jog every day?

Submitted by Phil on

Hello Phil

There’s no evidence that thinking about flashing lights triggers seizures. Tiredness can be a seizure trigger for many people with epilepsy, not just those with photosensitive epilepsy. Usually when people talk about tiredness triggering a seizure they mean the sort of tiredness they feel when they’ve not has as much sleep as usual, but it varies from person to person.

With the right support and safety precautions, most sport and leisure activities are safe for people with epilepsy. A very small number of people find that strenuous exercise increases their likelihood of having seizures. This shouldn’t mean they need to avoid exercise completely, but just to make sure they don’t push themselves too hard. You might find our sports and leisure page useful.


Epilepsy Action Helpline Team

Submitted by rich on

Hi, my name is katie. I am a type 1 diabetic using a pump since 2011. I was newly diagnosed back then due to having had a seizure from low blood glucose levels.
Since then I have been having these very strange and frightening episodes whenever myself and partner are in the car with my partner driving - if the sun is out and it passes through the trees, I get these terrible red patterns that flash very quickly in my eyes which make me jump and I feel as if I'm going to black out, and although I have never actually had a seizure while this is happening, I feel as though I'm going to have one. Does this mean anything?
Also, sometimes, if it's very bright outside when I leave my house, I can't see anything, just brightness, and I have to just stand where I am, not moving, until my eyes have adjusted to the light.
I haven't been to my gp about this yet because I feel foolish and don't want to waste his time. Can you help in telling me what these symptoms could possibly be? I am 54 years of age.
Thank you in anticipation. Katie

Submitted by Katie Ryan on

As a teenager I passed out at a disco that used strobe lights, nothing happened again for several years, until I was present at a Magic show that used strobe lights and I passed out again. Now as soon as I feel strange in similar circumstances I cover and close my eyes, asking people to tell me when it is over. I am okay with most flashing lights that are not strobes, but I have sometimes found the same experience with some lights. Until this Saturday that was the extent of my experience, that was when I visited my local Planetarium in Bristol. There were no flashing lights that I could discern, but I felt nauseous, which I have never experienced before, felt like car sickness or sea sickness, and at some points I felt the 'strobe light' effect coming on. No idea what was causing it. Has anyone else experienced this at a Planetarium, and was the nausea connected or something different.

Submitted by Billie Dale Wak... on

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